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The Maximum Glaciation in the Argentine Cordillera

By
Jorge Polanski
Jorge Polanski
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Published:
January 01, 1965

During the Pleistocene only the Argentine Cordillera was glaciated. Thus the hypothesis for an ice sheet in the extra-Andean arid zone is to be considered completely without foundation. The maximum glaciation of the Cordillera was probably the late Pleistocene (Würm, Wisconsin) and has almost obliterated the remains of the older glaciations in the mountains. The submontane gravel terraces do not show any genetic connection with Pleistocene climatic fluctuations; they owe their existence to the intermittent phases of the neotectonic rise of the Cordillera.

The Argentine loesses are only loess-like, ash-rich fine sands and silts, which were deposited in the warm-dry period of the Pliocene, the interglacial periods, and also during the postglacial. Consequently, the Argentine loess-like and predominantly eolian sediments are continental and semidesert formations and cannot be considered equivalents of the glacial loesses of the northern hemisphere.

The morainic topography of the maximum glaciation of the Cordillera changes with climatic zones. Three basically different periods can be distinguished:

  1. (1) In the south, in the humid Patagonian Cordillera, lies the Patagonian section with the typical alpine-moraine landscape. The end moraine surrounds large lakes and is a source for terraced outwash to the east.

  2. (2) The central Andean section penetrates the dry Cordillera. The alpine type disappears almost entirely from the surface, and there are neither moraines nor lakes. The short glacial tongues were and still are today buried under a heavy cover of superglacial debris, which during the wastage of the glacier remained in place as valley fill whose surface is an amorphous detritus accumulation. The meltwaters flowed in subterranean channels, which emerged at the end of the valley fill and, as well-filtered clear streams, left no outwash.

  3. (3) The northernmost section lies in the dry Pre-puna range and forms a paternoster series of little cirque moraines, which, half destroyed, tend to lie at high elevations.

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GSA Special Papers

International Studies on the Quaternary: Papers Prepared on the Occasion of the VII Congress of the International Association for Quaternary Research Boulder, Colorado, 1965

H. E. Wright, Jr.
H. E. Wright, Jr.
Editors
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David G. Frey
David G. Frey
Editors
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Geological Society of America
Volume
84
ISBN print:
9780813720845
Publication date:
January 01, 1965

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